Menthanol extraction of polar organic compounds and modifier compounds from poly(arylene sulfide) polymer and oligomer streams

ABSTRACT

A process is provided to recover at least one modifier compound and at least one polar organic compound from a poly(arylene sulfide) reaction mixture comprising high molecular weight poly(arylene sulfide), low molecular weight poly(arylene sulfide), cyclic and linear poly(arylene sulfide) oligomers, at least one polar organic compound, at least one modifier compound, and an alkali metal halide by-product.

FIELD OF INVENTION

This invention relates to the field of processes utilizing methanol forextracting at least one polar organic compound, hereinafter referred toas “POC”, and at least one modifier compound from poly(arylene sulfide)polymer and oligomer streams.

BACKGROUND OF THE INVENTION

The production of poly(arylene sulfide), hereinafter referred to asP(AS), for a variety of industrial and commercial uses has been knownfor some time. P(AS) is moldable into various articles including, butnot limited to, parts, films, and fibers by means of, for example,injection molding and extrusion molding techniques. These articles haveutility in a variety of applications where heat and chemical resistanceproperties are desired. For example, P(AS) can be utilized as a materialfor preparing electrical and electronic parts and automotive parts.

Generally, high molecular weight P(AS) is prepared by contactingreactants comprising at least one dihalogenated aromatic compound, atleast one POC, and at least one sulfur source, at least one base, and atleast one modifier compound under polymerization conditions.

There are several problems associated with the current synthesis ofP(AS) that cause the production expenses to be high. First, in bothquench and flash P(AS) processes, modifiers utilized to synthesize thehigh molecular weight P(AS) are used once in the process and are notcaptured and recycled for subsequent use. This constitutes a greatexpense in the production of P(AS) due to the higher feedstock and wastedisposal expense. Secondly, POC utilized in the process can berecovered, but often at a high cost. For example, n-hexanol is oftenutilized to extract N-methyl-2-pyrrolidone (NMP), a common POC.Operating the hexanol extractor system can require the handling of asmuch as 30 to 40 pounds of n-hexanol per pound of P(AS) produced causinghigh equipment and operational costs.

This invention provides a P(AS) process for recovering modifier compoundand POC, which can greatly reduce the feedstock and disposal expensecompared to current P(AS) processes. As a result of these improvements,the P(AS) produced by this invention has higher purity than thatproduced from current P(AS) processes.

SUMMARY OF INVENTION

It is an object of this invention to provide a process to recover atleast one modifier compound and at least one POC from a quench processreaction mixture or flash process reaction mixture.

It is another object of this invention to provide a process thatproduces high purity, high molecular weight P(AS) product.

In accordance with one embodiment of the present invention, a process isprovided to recover at least one POC and at least one modifier from aquench process reaction mixture comprising high molecular weight P(AS),low molecular weight P(AS), cyclic and linear P(AS) oligomers, at leastone POC, at least one modifier compound, and an alkali metal halideby-product.

The process comprises:

1) contacting the quench process reaction mixture with methanol toproduce a quench process methanol-rich mixture;

2) separating the quench process methanol-rich mixture to produce a highmolecular weight P(AS) product, a recycle mixture, and optionally, a lowmolecular weight P(AS) stream;

wherein the recycle mixture comprises methanol, POC, and modifiercompound;

wherein the low molecular weight P(AS) stream comprises low molecularweight P(AS) and cyclic and linear P(AS) oligomers.

In accordance with a second embodiment of this invention, a process isprovided to recover at least one POC and at least one modifier from aquench process reaction mixture comprising high molecular weight P(AS),low molecular weight P(AS), cyclic and linear P(AS) oligomers, at leastone POC, at least one modifier, and an alkali metal halide by-product.The process comprises:

1) contacting the quench process reaction mixture with at least one POCat a temperature sufficient to dissolve substantially all of the lowmolecular weight P(AS) and cyclic and linear oligomers to produce aquench process POC-rich mixture;

2) separating the quench process POC-rich mixture to produce a quenchprocess solid stream and a quench process liquid stream;

wherein the quench process solid stream is in a substantially solid formand comprises high molecular weight P(AS), POC, modifier compound, andalkali metal halide by-product;

wherein the quench process liquid stream is in a substantially liquidform and comprises substantially all of the low molecular weight P(AS)and cyclic and linear P(AS) oligomers, POC, and modifier compound;

3) contacting the quench process solid stream with methanol to produce aquench process methanol-rich P(AS) product mixture; and

4) separating the quench process methanol-rich P(AS) product mixture toproduce a high molecular weight P(AS) product and a recycle mixture;

wherein the recycle mixture comprises methanol, POC, and modifiercompound.

In accordance with a third embodiment of this invention, a process isprovided to recover at least one POC and at least one modifier compoundfrom a flash process reaction mixture comprising high molecular weightP(AS), low molecular weight P(AS), cyclic and linear P(AS) oligomers, atleast one POC, at least one modifier, and an alkali metal halideby-product.

The process comprises:

1) contacting the flash process reaction mixture with methanol toproduce a flash process methanol-rich mixture;

2) separating the flash process methanol-rich mixture to produce a P(AS)stream and a recycle mixture;

wherein the recycle mixture comprises methanol, POC, and modifiercompound.

In accordance with a fourth embodiment of this invention, a process isprovided to recover at least one POC and at least one modifier compoundfrom a flash process reaction mixture comprising high molecular weightP(AS), low molecular weight P(AS), cyclic and linear P(AS) oligomers, atleast one POC, at least one modifier, and an alkali metal halideby-product.

The process comprises:

1) contacting the flash process reaction mixture with at least one POCat a temperature sufficient to dissolve a majority of the low molecularweight P(AS) and cyclic and linear oligomers to produce a flash processPOC-rich mixture;

2) separating the flash process POC-rich mixture to produce a flashprocess solid stream and a flash process liquid stream;

wherein the flash process solid stream is in a substantially solid formand comprises insoluble P(AS), the POC, modifier compound, and alkalimetal halide by-product;

wherein the flash process liquid stream is in a substantially liquidform and comprises soluble P(AS) and POC;

3) contacting the flash process solid stream with methanol to produce aflash process methanol-rich P(AS) product mixture; and

4) separating the flash process methanol-rich P(AS) product mixture toproduce a high molecular weight P(AS) product and a recycle mixture;

wherein the recycle mixture comprises methanol, POC, and modifiercompound.

DETAILED DESCRIPTION OF INVENTION

Different embodiments of this invention provide processes to recover atleast one modifier compound and at least one POC from a P(AS) reactionmixture.

P(AS) reaction mixtures useful in this invention can be produced by anymethod known in the art. Examples of the reaction mixtures useful inthis invention are those prepared according to U.S. Pat. Nos. 3,919,177,4,038,261, 4,038,262, 4,116,947, 4,282,347 and 4,350,810, the entiredisclosures of which are herein incorporated by reference. The U.S. Pat.No. 4,038,261 patent discloses poly(phenylene sulfide).

Generally, reaction mixtures useful in this invention are prepared bycontacting a halogenated aromatic compound, at least one POC, at leastone sulfur source, at least one base, and at least one modifier compoundunder polymerization reaction conditions to product high molecularweight P(AS). The use of modifier compounds in the production of highmolecular weight P(AS) is disclosed in U.S. Pat. No. 5,334,701, hereinincorporated by reference.

As used herein, the term “high molecular weight” or “high molecularweight P(AS)” means all P(AS) molecules having molecular weights highenough to be commercially desirable and useable in an uncured state.Generally, the melt flow of a high molecular weight P(AS) is less thanabout 3,000 g/10 minutes. As used herein, the term “low molecularweight” or “low molecular weight P(AS)” means all P(AS) molecules havingmolecular weights too low to be commercially desirable and, thus, notuseable in an uncured state. Generally, the melt flow of a low molecularweight P(AS) is greater than about 3,000 g/10 minutes.

Halogenated aromatic compounds suitable for producing reaction mixturesuseful in this invention can be represented by the formula

wherein X is a halogen, and R is selected from the group consisting ofhydrogen, halogens, and alkyl, cycloalkyl, aryl, alkylaryl, andarylalkyl radicals having from about 6 to about 24 carbon atoms.Exemplary halogenated aromatic compounds include, but are not limitedto, p-dichlorobenzene (DCB), p-dibromobenzene, p-diiodobenzene,1-chloro-4-bromobenzene, 1-chloro-4-iodobenzene, 1-bromo-4-iodobenzene,2,5-dichlorotoluene, 2,5-dichloro-p-xylene,1-ethyl-4-isopropyl-2,5-dibromobenzene,1,2,4,5-tetramethyl-3,6-dichlorobenzene,1-butyl-4-cyclohexyl-2,5-dibromobenzene,1-hexyl-3-dodecyl-2,5-dichlorobenzene, 1-octadecyl-2,4-diiodobenzene,1-chloro-2-phenyl-4-bromobenzene, 1,4-diiodo-2-p-tolylbenzene,1,4-dibromo-2-benzylbenzene,1-octyl-4-(3-methylcyclopentyl)-2,5-dichlorobenzene, and mixturesthereof. The preferred halogenated aromatic compound to produce thereaction mixture is DCB, due to availability, ease of use, and highpolymerization productivity.

At least one POC must be utilized to produce the reaction mixture.Exemplary POCs include, but are not limited to, cyclic or acyclicorganic amides having from about 1 to about 10 carbon atoms permolecule. Exemplary POCs are selected from the group consisting offormamide, acetamide, N-methylformamide, N,N-dimethylformamide,N,N-dimethylacetamide, N-ethylpropionamide, N,N-dipropylbutyramide,2-pyrrolidone, N-methyl-2-pyrrolidone (NMP), ε-caprolactam,N-methyl-ε-caprolactam, N,N′-ethylenedi-2-pyrrolidone,hexamethylphosphoramide, tetramethylurea, and mixtures thereof. Thepreferred POC for use in producing the reaction mixture is NMP due toavailability and ease of use.

Any suitable source of sulfur can be used to produce the reactionmixture. Exemplary sulfur sources are selected from the group consistingof thiosulfates, substituted and unsubstituted thioureas, cyclic andacyclic thioamides, thiocarbamates, thiocarbonates, trithiocarbonates,organic sulfur-containing compounds selected from mercaptans,mercaptides and sulfides, hydrogen sulfide, phosphorous pentasulfide,carbon disulfides and carbon oxysulfides, and alkali metal sulfides andbisulfides, and mixtures thereof. It generally is preferred to use analkali metal bisulfide as a source of sulfur wherein the alkali metal isselected from the group consisting of sodium, potassium, lithium,rubidium, and cesium due to availability and ease of use. The preferredalkali metal bisulfide is sodium bisulfide (NaSH) due to availabilityand low cost.

Suitable bases to produce the reaction mixture are alkali metalhydroxides selected from the group consisting of lithium hydroxide,sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesiumhydroxide, and mixtures thereof. If desired, the base can be producedin-situ by reaction of the corresponding oxide with water. The preferredbase is sodium hydroxide (NaOH) due to availability and ease of use.

At least one modifier compound is utilized to produce the reactionmixture. The modifier compound is selected from the group consisting ofalkali metal carboxylates, alkali metal halides which are soluble inPOC, water, and mixtures thereof.

Alkali metal carboxylate modifier compounds can be represented by theformula R¹-COOM, where R¹ of the modifier compound is a hydrocarbylradical having from 1 to about 20 carbon atoms and is selected from thegroup consisting of alkyl, cycloalkyl, and aryl and combinations thereofsuch as alkylaryl, alkylcycloalkyl, cycloalkylalkyl, arylalkyl,arylcycloalkyl, alkylarylalkyl and alkylcycloalkylalkyl, and M is analkali metal selected from the group consisting of lithium, sodium,potassium, rubidium and cesium. Preferably, in order to have a moreefficient polymerization reaction, R¹ is an alkyl radical having from 1to about 6 carbon atoms or a phenyl radical, and M is lithium or sodium.If desired, the alkali metal carboxylate modifier compound can beemployed as a hydrate or as a solution or dispersion in water. Ifdesired, the alkali metal carboxylate modifier compound can be producedin-situ by a reaction of the corresponding carboxylic acid and an alkalimetal hydroxide or carbonate.

Suitable alkali metal carboxylate modifier compounds which can beemployed to produce the reaction mixture are selected from the groupconsisting of lithium acetate, sodium acetate, potassium acetate,lithium propionate, sodium propionate, lithium 2-methylpropionate,rubidium butyrate, lithium valerate, sodium valerate, cesium hexanoate,lithium heptanoate, lithium 2-methyloctanoate, potassium dodecanoate,rubidium 4-ethyltetradecanoate, sodium octadecanoate, sodiumheneicosanoate, lithium cyclohexanecarboxylate, cesiumcyclododecanecarboxylate, sodium 3-methylcyclopentanecarboxylate,potassium cyclohexylacetate, potassium benzoate, lithium benzoate,sodium benzoate, potassium m-toluate, lithium phenylacetate, sodium4-phenylcyclohexanecarboxylate, potassium p-tolylacetate, lithium4-ethylcyclohexylacetate, and mixtures thereof. The preferred alkalimetal carboxylate modifier compound for use in this invention is sodiumacetate (NaOAc) due to availability, low cost, and effectiveness.

Alkali metal halide modifier compounds useful in this invention arethose which are soluble in the POC or can be made soluble in a mixtureof the POC and another modifier compound. For example, lithium chloridecan be useful as the modifier compound, since it is soluble in certainPOCs, such as, for example, NMP.

At the termination of the polymerization reaction, the reaction mixturecomprises high molecular weight P(AS), low molecular weight P(AS),cyclic and linear P(AS) oligomers, at least one POC, at least onemodifier compound, an alkali metal halide by-product, and water. Thereaction mixture is in a substantially two-phase liquid form at reactiontemperatures. Alkali metal halide by-product is present as aprecipitate.

In a first embodiment of this invention, a process is provided torecover at least one POC and at least one modifier from a quench processreaction mixture comprising high molecular weight P(AS), low molecularweight P(AS), cyclic and linear P(AS) oligomers, at least one POC, atleast one modifier compound, and an alkali metal halide by-product. In aquench process, the reaction mixture is cooled to a temperature belowabout 240° C., preferably in a range of 100° C. to 240° C. The quenchrecovery process is disclosed in U.S. Pat. Nos. 4,415,729 and 5,128,445,both of which are herein incorporated by reference.

The first step of the first embodiment comprises contacting the quenchprocess reaction mixture with methanol to produce a quench processmethanol-rich mixture. Methanol must be used to remove a majority of thePOC and modifier compound from the quench process reaction mixture.

Generally, the quench process reaction mixture is contacted withmethanol at a temperature sufficient to remove a majority of themodifier compound and POC. Preferably, the quench process reactionstream is contacted with methanol at a temperature in a range of about20° C. to about 50° C. In this temperature range, losses of methanol areminimized. Generally, about 1.5 to about 15 pounds of methanol per poundof P(AS) are used to recover the modifier compound and the POC.Preferably, about 7 to about 11 pounds of methanol per pound of P(AS)are used, and most preferably, 8 to 10 pounds of methanol per pound ofP(AS). The preferred ranges are established to adequately andeconomically remove the modifier compound and POC from the quenchprocess reaction mixture.

Generally, the quench process reaction mixture is contacted withmethanol a sufficient number of times to adequately remove a majority ofthe modifier compound and the POC. Preferably, the quench processreaction mixture is contacted with methanol in at least threerepetitions. The quench process reaction mixture can be contacted withmethanol by any method known in the art. For example, counter-currentwashing techniques can be utilized. In counter-current washing, thequench process reaction mixture flows in one direction, and methanolflows in the opposite direction.

The second step of the first embodiment of this invention comprisesseparating the quench process methanol-rich mixture to produce a highmolecular weight P(AS) product, a recycle mixture, and optionally, a lowmolecular weight P(AS) stream. The recycle mixture comprises methanol,POC, and modifier compound. The low molecular weight P(AS) streamcomprises low molecular weight P(AS) and cyclic and linear P(AS)oligomers.

The separation can be accomplished by any process known in the art. Forexample, such processes can include, but are not limited to, screening,centrifugation, and filtration.

The high molecular weight P(AS) product can be contacted with water toproduce a water-washed high molecular weight P(AS) product and an alkalimetal halide by-product stream. The alkali metal halide by-productstream comprises water, methanol, and alkali metal halide by-product.The water-washed high molecular weight P(AS) product and alkali metalhalide by-product then are separated by any process known in the art.For example, such processes can include, but are not limited to,centrifugation, filtration, and screening.

Various additives can be mixed with the high molecular weight P(AS)product obtained in the present invention. Common additives include, butare not limited to, inorganic fillers (e.g., glass fiber, carbon fiber,titanium oxide, calcium carbonate, etc.) antioxidants, heat stabilizers,ultraviolet absorbents, coloring agents, and mixtures thereof.

If necessary, other polymers such as, for example, polyamides,polysulfones, polycarbonates, polyether sulfones, polyethyleneterephthalates, polybutylene terephthalates, polyethylenes,polypropylenes, polytetrafluoroethylenes, polyether ester elastomers,and polyether amide elastomers also can be added.

If desired, the high molecular weight P(AS) product can also be cured byheating at temperatures up to about 480° C. to provide cured productshaving improved properties and high thermal stability and good chemicalresistance.

The recycle mixture can be separated in a first separation zone to yieldmethanol and a recycle feedstock mixture. The recycle feedstock mixturecomprises POC and modifier compound. The first separation zone cancomprise any means known in the art to separate the recycle mixture.Preferably, a fractionation column is utilized at sufficienttemperatures and pressures to allow substantially all of the methanol tobe recovered in one stream and the recycle feedstock mixture to berecovered in a different stream. Both the methanol and recycle feedstockmixture can be reused.

Removal of substantially all of the methanol from the recycle mixturecan cause the modifier compound to precipitate. For example, sincesodium acetate is not appreciably soluble in NMP, sodium acetate canprecipitate when the methanol is removed. Preferably, the separating isconducted in the presence of water in order for the modifier compound toform a solution with water and the POC, so that the solution can behandled more easily. Generally, about 2 to about 10 moles of water permole of modifier compound are added to adequately form the solution.Preferably, about 3 to about 8 moles of water per mole of modifiercompound are added, and most preferably, 4 moles to 6 moles of water permole of modifier compound are added to adequately form the solution.

The alkali metal halide by-product stream can be separated in a secondseparation zone to produce methanol and a brine stream, wherein thebrine stream comprises water and alkali metal halide by-product. Thesecond separation zone can comprise any means known in the art toseparate the alkali metal halide by-product stream. Preferably, afractionation column is utilized at sufficient temperatures andpressures to allow methanol to be recovered in one stream and the brineto be recovered in a different stream. The methanol can be reused.

In a second embodiment of this invention, another process to recover atleast one POC and at least one modifier from a quench process reactionmixture is provided. The first step of the second embodiment comprisescontacting the quench process reaction mixture with at least one POC ata temperature sufficient to dissolve substantially all of the lowmolecular weight P(AS) and cyclic and linear oligomers to produce aquench process POC-rich mixture.

The POC can be any POC previously discussed in this disclosure, andpreferably, is NMP due to its availability and ease of use. Generally,the POC is at a temperature in a range of about 100° C. to about 220° C.Preferably, the POC is at a temperature in a range of about 135° C. toabout 200° C., most preferably, 150° C. to 175° C. At temperatures belowabout 135° C., the solubility of low molecular weight P(AS) in POC issignificantly lower. At temperatures above 200° C., if NMP is used asthe POC, the vapor pressure of NMP can require that the contacting beconducted in a pressure vessel. The higher the temperature of contactingthe reaction mixture with the POC, the greater the amount of lowmolecular weight P(AS) and linear and cyclic oligomers that can beremoved from the reaction mixture.

Preferably, sufficient POC can be added during contacting to produce aPOC-rich mixture that adequately dissolves the low molecular weightP(AS) and linear and cyclic oligomers. This allows removal ofsubstantially all of the low molecular weight P(AS) and linear andcyclic oligomers from the reaction mixture, thus producing a higherpurity high molecular weight P(AS) product. Preferably, about 2 to about7 moles of POC per mole of P(AS) are added for adequate removal. Mostpreferably, 3 to 6 moles of POC per mole of P(AS) are used.

Generally, the quench process reaction mixture is contacted with the POCat a temperature sufficient to dissolve substantially all of the lowmolecular weight P(AS) and cyclic and linear oligomers. The quenchprocess reaction mixture can be contacted with the POC multiple times tofurther remove the low molecular weight P(AS) and linear and cyclicoligomers.

Contacting times between the quench process reaction mixture and the POCshould be sufficient to dissolve substantially all of the low molecularweight P(AS) and cyclic and linear oligomers. Contact times as short as1 minute can be adequate to remove low molecular weight P(AS) and linearand cyclic oligomers from the quench process reaction mixture.

The second step in the second embodiment comprises separating the quenchprocess POC-rich mixture to produce a quench process solid stream and aquench process liquid stream. The quench process solid stream is in asubstantially solid form and comprises the high molecular weight P(AS),the POC, modifier compound, and the alkali metal halide by-product Thehigh molecular weight P(AS) is in a substantially granular form. Thequench process liquid stream is in a substantially liquid form andcomprises the POC, the modifier compound, and substantially all of thelow molecular weight P(AS) and cyclic and linear P(AS) oligomers. Thelow molecular weight P(AS) is in the form of the solids.

The separation should be completed at a temperature similar to thetemperature at which the POC was contacted with the quench processreaction mixture. If the quench process POC-rich mixture is cooled, thelow molecular weight P(AS) and linear and cyclic oligomers canprecipitate on the high molecular weight P(AS) product, therebydecreasing the efficiency of removal. This separation can beaccomplished by any process known in the art. For example, screening canbe used.

The third step of the second embodiment comprises contacting the quenchprocess solid stream with methanol to produce a quench processmethanol-rich P(AS) product mixture. Methanol must be used to remove amajority of the POC and modifier compound from the quench process solidstream.

Generally, the quench process solid stream is contacted with methanol ata temperature sufficient to remove a majority of the modifier compoundand POC. Preferably, the quench process solid stream is contacted withmethanol at a temperature in a range of about 20° C. to about 50° C. Inthis temperature range, losses of methanol are minimized. Generally,about 1.5 to about 15 pounds of methanol per pound of P(AS) are used torecover the modifier compound and the POC. Preferably, about 7 to about11 pounds of methanol per pound of P(AS) are used, and most preferably,8 to 10 pounds of methanol per pound of P(AS). The preferred ranges areestablished to adequately and economically remove the modifier compoundand POC from the quench process solid stream.

Generally, the quench process solid stream is contacted with methanol asufficient number of times to adequately remove a majority of themodifier compound and the POC. Preferably, the quench process solidstream is contacted with methanol in at least three repetitions. Thequench process solid stream can be contacted with methanol by any methodknown in the art. For example, counter-current washing techniques can beutilized. In counter-current washing, the quench process solid streamflows in one direction, and methanol flows in the opposite direction.

The fourth step of the second embodiment comprises separating the quenchprocess methanol-rich P(AS) product mixture to produce a high molecularweight P(AS) product and a recycle mixture. The recycle mixturecomprises methanol, POC, and modifier compound.

The recycle mixture can be separated in the first separation zone asdiscussed previously in this disclosure.

The high molecular weight P(AS) product can be contacted with water toproduce a water-washed high molecular weight P(AS) product and an alkalimetal halide by-product stream. The alkali metal halide by-productstream can be treated in the second separation zone as discussedpreviously in this disclosure.

In a third embodiment of this invention, a process is provided torecover methanol, sodium acetate, and POC from the quench process liquidstream. The first step in the third embodiment comprises contacting thequench process liquid stream with methanol to produce a quench processmethanol-rich low molecular weight P(AS) mixture. The same conditions asused in contacting the quench process solid stream with methanol can beused.

The second step in the third embodiment comprises separating the quenchprocess methanol-rich low molecular weight P(AS) mixture to produce alow molecular weight P(AS) product and a recycle stream. The recyclestream comprises the methanol, POC, and modifier compound. The lowmolecular weight P(AS) product comprises the low molecular weight P(AS)and cyclic and linear P(AS) oligomers. The separation can beaccomplished by any process known in the art. For example, suchprocesses can include, but are not limited to, centrifugation andfiltration.

The recycle mixture can be separated in the first separation zone asdiscussed previously in this disclosure.

The low molecular weight P(AS) product can be contacted with water toproduce a water-washed low molecular weight P(AS) product and an alkalimetal halide by-product stream. The alkali metal halide by-productstream can be treated in the second separation zone as discussedpreviously in this disclosure.

In a fourth embodiment of this invention, a process to recover at leastone POC and at least one modifier from a flash process reaction mixtureis provided.

In a flash recovery process, the reaction mixture is subjected to lowpressure evaporation to remove a majority of the POC. If desired, thePOC can be recycled for subsequent polymerizations after condensation.After flash recovery, a flash process reaction mixture is producedcomprising high molecular weight PAS, low molecular weight P(AS), cyclicand linear P(AS) oligomers, alkali metal halide by-product, modifiercompound, and POC.

Conditions employed during the flash recovery process can varyappreciably but preferably reduced pressures can be employed. Generally,pressure in the flash recovery process should be sufficient to evaporateabout 30% to about 90% of the POC, typically, a pressure reduction ofapproximately 200 psig is required. Pressures as low as 0.05 psig can beemployed although the pressure generally is not below one psig.Temperatures of the reaction mixture from the reactor usually range fromabout 200° C. to about 325° C. Temperatures in a flash recovery vesselafter pressure reduction generally range from about 90° C. to about 200°C. depending upon the pressure in the flash recovery vessel.

Various methods of flash recovery of P(AS) are known in the artincluding U.S. Pat. Nos. 3,478,000 and 3,956,060, both of which areherein incorporated by reference.

The first step of the fourth embodiment comprises contacting the flashprocess reaction mixture with methanol to produce a flash processmethanol-rich mixture. The procedures for contacting the flash processreaction mixture with methanol is the same as discussed previously forthe quench process reaction mixture.

The second step of the third embodiment comprises separating the flashprocess methanol-rich mixture to produce a P(AS) product and a recyclemixture. The recycle mixture comprises methanol, POC, and modifiercompound. The P(AS) product comprises high molecular weight P(AS), lowmolecular weight P(AS), and cyclic and linear P(AS) oligomers. Theseparation can be accomplished by any process known in the art. Forexample, such processes can include, but are not limited to,centrifugation and filtration.

The recycle mixture can be separated in the first separation zone asdiscussed previously in this disclosure.

The P(AS) product can be contacted with water to produce a water-washedP(AS) product and an alkali metal halide by-product stream. The alkalimetal halide by-product stream can be treated in the second separationzone as discussed previously in this disclosure.

In a fifth embodiment of this invention, a process is provided torecover at least one POC and at least one modifier compound from a flashprocess reaction mixture comprising high molecular weight P(AS), lowmolecular weight P(AS), cyclic and linear P(AS) oligomers, at least onePOC, at least one modifier, and an alkali metal halide by-product.

The first step of the fifth embodiment comprises contacting the flashprocess reaction mixture with at least one POC at a temperaturesufficient to dissolve a majority of the low molecular weight P(AS) andcyclic and linear oligomers to produce a flash process POC-rich mixture.The flash process reaction mixture is contacted with POC by the samemethod discussed previously for the quench process reaction mixture.

The second step of the fifth embodiment comprises separating the flashprocess POC-rich mixture to produce a flash process solid stream and aflash process liquid stream. The flash process solid stream is in asubstantially solid form and comprises insoluble P(AS), the POC,modifier compound, and the alkali metal halide by-product. The flashprocess liquid stream is in a substantially liquid form and comprisessoluble P(AS) and the POC. The separating can be accomplished by anyprocess known in the art. For example, such processes can include, butare not limited to, centrifugation and filtration.

The third step of the fifth embodiment comprises contacting the flashprocess solid stream with methanol to produce a flash processmethanol-rich P(AS) product mixture. The flash process solid stream iscontacted with methanol by the same method discussed previously for thequench process solid stream.

The fourth step of the fifth embodiment comprises separating the flashprocess methanol-rich P(AS) product mixture to produce a high molecularweight P(AS) product and a recycle mixture. The recycle mixturecomprises methanol, the POC, and modifier compound. The separation canbe accomplished by any process known in the art. For example, suchprocesses can include, but are not limited to, centrifugation andfiltration.

The recycle mixture can be separated in the first separation zone asdiscussed previously in this disclosure.

The high molecular weight P(AS) product can be contacted with water toproduce a water-washed high molecular weight P(AS) product and an alkalimetal halide by-product stream. The alkali metal halide by-productstream can be treated in the second separation zone as discussedpreviously in this disclosure.

EXAMPLES Example 1

The following example shows that methanol can be separated from NMP byfractionation.

75 grams of methanol and 75 grams of NMP (Fisher Purified Grade) wereadded to a 250 milliliter round bottom flask containing boiling chips.The flask was attached to a vacuum jacketed fractionating column. Heatwas applied to the round bottom flask using a heating mantle. The vacuumjacketed fractionating column heated slowly due to internal reflux. Avapor started to flow through a condenser and into a receiver to producean overhead liquid stream. The flow of vapor slowed until thetemperature of the fractionating column increased with further heatingof the round bottom flask. Upon reaching the boiling point of NMP, theflow of the overhead liquid stream resumed. Then, the vacuum jacketedfractionating column was cooled to room temperature. Heating of theround bottom flask was then terminated.

Fractions of the overhead liquid stream were collected in small vials.These fractions and a sample of liquid remaining in the round bottomflask were analyzed using gas chromatography. Analyses of the fractionsindicated that 99.547% by weight of the overhead liquid stream collectedwas methanol and 0.453% by weight was NMP. Analysis of the sample of theliquid in the round bottom flask was found to be 100% NMP.

Thus, methanol can be removed efficiently from NMP.

Example 2

This example shows separation of a recycle mixture to produce methanoland a recycle feedstock mixture.

A recycle mixture containing 78.03 wt. % NMP, 15.90 wt. % methanol, and6.07 wt. % sodium acetate was fed to a laboratory continuousdistillation kettle at a continuous rate of 504.20 cm³/hr. A smallquantity of NMP was initially added to the kettle. The kettle was heateduntil the recycle mixture reached reflux at which point the kettletemperature was approximately 210° C., and the temperature throughoutthe column was about 66-208° C. A methanol stream was recovered throughan overhead splitter and routed to an overhead condenser, and then to anoverhead receiver. The overhead splitter was set to collect for 0.2minutes and to discharge to the overhead receiver for 5 seconds. Therecycle feedstock mixture was pumped from the kettle at a rate of 87.40cm³/hr. After approximately one hour, samples were collected of themethanol stream and the recycle feedstock mixture in the bottom of thekettle.

The recycle feedstock mixture and methanol stream were analyzed by gaschromatography. The recycle feedstock mixture contained 99.50 wt. % NMP,0.29 wt. % methanol, and 0.21 wt. % of other compounds. The methanolstream contained 99.73 wt % methanol, 0.08 wt. % NMP, and 0.19 wt. %other compounds.

During the experiment, it was noted by visual inspection that the sodiumacetate accumulated in the bottom of the distillation kettle and column.

This example teaches that methanol can be removed efficiently fromsodium acetate and NMP.

Example 3

This example demonstrates that water can be added to a recycle mixtureto help prevent the accumulation of sodium acetate in the bottom of thedistillation kettle.

The same procedures as disclosed in Example 2 were utilized except therecycle mixture contained 14.60 wt. % methanol, 72.00 wt. % NMP, 4.60wt. % sodium acetate, and 8.8 wt. % water. The kettle temperature wasapproximately 190-198° C., and the temperature throughout the column wasapproximately 68-102° C. The overhead splitter was set to collect for0.3 minutes and to discharge to the overhead receiver for 5 seconds.

Samples of the methanol stream and the recycled feedstock stream werecollected after 8.66 hours of distillation and analyzed by gaschromatography. The recycle feedstock mixture contained 97.53 wt. % NMP,0.00 wt. % methanol, 1.63 wt. % water, and 0.16 wt. % of othercompounds. The methanol stream contained 97.36 wt % methanol, 0.03 wt. %NMP, 2.60 wt. % water, and 0.02 wt. % other compounds. Negligibleprecipitation of sodium acetate was observed in the bottom of thedistillation kettle. Ion chromatograph was used to determine the amountof sodium acetate in the recycle feedstock mixture. 0.69% by weightsodium acetate was found.

This experiment illustrates that the addition of water to the recyclemixture substantially prevents the accumulation of sodium acetate in thebottom of the distillation kettle. An exact mass balance was notachieved in this experiment for the sodium acetate since thedistillation was not continued for a long enough duration.

While this invention has been described in detail for the purpose ofillustration, it is not intended to be limited thereby but is intendedto cover all changes and modifications within the spirit and scopethereof.

What is claimed is:
 1. A process to recover at least one polar organiccompound and at least one modifier from a quench process reactionmixture comprising high molecular weight poly(arylene sulfide), lowmolecular weight poly(arylene sulfide), cyclic and linear poly(arylenesulfide) oligomers, at least one polar organic compound, at least onemodifier, and an alkali metal halide by-product, said processcomprising: 1) contacting said quench process reaction mixture withadditional polar organic compound at a temperature sufficient todissolve substantially all of said low molecular weight poly(arylenesulfide) and cyclic and linear oligomers to produce a quench processpolar organic compound-rich mixture; 2) separating said quench processpolar organic compound-rich mixture to produce a quench process solidstream and a quench process liquid stream; wherein said quench processsolid stream is in a substantially solid form and comprises said highmolecular weight poly(arylene sulfide), polar organic compound, aportion of said modifier compound, and a portion of said alkali metalhalide by-product; wherein said quench process liquid stream is in asubstantially liquid form and comprises substantially all of said lowmolecular weight poly(arylene sulfide) and cyclic and linearpoly(arylene sulfide) oligomers, polar organic compound, and a portionof said modifier compound; 3) contacting said quench process solidstream with methanol to produce a quench process methanol-richpoly(arylene sulfide) product mixture; and 4) separating said quenchprocess methanol-rich poly(arylene sulfide) product mixture to produce ahigh molecular weight poly(arylene sulfide) product and a recyclemixture; wherein said recycle mixture comprises methanol, polar organiccompound, and modifier compound; 5) separating said recycle mixture in afirst separation zone to yield methanol and a recycle feedstock mixture;wherein said recycle feedstock mixture comprises polar organic compoundand modifier compound.
 2. A process according to claim 1 furthercomprising contacting said high molecular weight poly(arylene sulfide)product with water to produce a water-washed high molecular weightpoly(arylene sulfide) product and an alkali metal halide by-productstream; wherein said alkali metal halide by-product stream compriseswater, methanol, and a portion of said alkali metal halide by-product.3. A process according to claim 2 further comprising separating saidalkali metal halide by-product stream in a second separation zone toproduce methanol and a brine stream; wherein said brine stream compriseswater and alkali metal halide by-product.
 4. A process according toclaim 1 wherein said poly(arylene sulfide) is poly(phenylene sulfide)and wherein said at least one polar organic compound and said additionalpolar organic compounds are NMP.
 5. A process according to claim 1wherein methanol and said recycle feedstock mixture is reused.
 6. Aprocess to recover at least one polar organic compound and at least onemodifier compound from a flash process reaction mixture comprising highmolecular weight poly(arylene sulfide), low molecular weightpoly(arylene sulfide), cyclic and linear poly(arylene sulfide)oligomers, at least one polar organic compound, at least one modifier,and an alkali metal halide by-product, said process comprising: 1)contacting said flash process reaction mixture with additional polarorganic compound at a temperature sufficient to dissolve a majority ofsaid low molecular weight poly(arylene sulfide) and cyclic and linearoligomers to produce a flash process polar organic compound-richmixture; 2) separating said flash process polar organic compound-richmixture to produce a flash process solid stream and a flash processliquid stream; wherein said flash process solid stream is in asubstantially solid form and comprises insoluble poly(arylene sulfide),polar organic compound, a portion of said modifier compound, and aportion of said alkali metal halide by-product; wherein said flashprocess liquid stream is in a substantially liquid form and comprisessoluble poly(arylene sulfide) and polar organic compound; 3) contactingsaid flash process solid stream with methanol to produce a flash processmethanol-rich poly(arylene sulfide) product mixture; and 4) separatingsaid flash process methanol-rich poly(arylene sulfide) product mixtureto produce a high molecular weight poly(arylene sulfide) product andrecycle mixture; wherein said recycle mixture comprises methanol, polarorganic compound, and modifier compound; 5) separating said recyclemixture in a first separation zone to yield methanol and a recyclefeedstock mixture; wherein said recycle feedstock mixture comprisespolar organic compound and modifier compound.
 7. A process according toclaim 6 further comprising contacting said high molecular weightpoly(arylene sulfide) product with water to produce a water-washed highmolecular weight poly(arylene sulfide) product and an alkali metalhalide by-product stream; wherein said alkali metal halide by-productstream comprises water, methanol, and said alkali metal halideby-product.
 8. A process according to claim 7 further comprisingseparating said alkali metal halide by-product stream in a secondseparation zone to produce methanol and a brine stream; wherein saidbrine stream comprises water and alkali metal halide by-product.
 9. Aprocess according to claim 6 further comprising recycling said flashprocess liquid stream to a poly(arylene sulfide) polymerization process.10. A process according to claim 6 wherein said separating in said firstseparation zone is carried out in the presence of water.
 11. A processaccording to claim 6 wherein said poly(arylene sulfide) ispoly(phenylene sulfide) and wherein said at least one polar organiccompound and said additional polar organic compounds are NMP.
 12. Aprocess according to claim 6 wherein methanol and said recycle feedstockmixture is reused.
 13. A process to recover at least one polar organiccompound and at least one modifier from a quench process reactionmixture comprising high molecular weight poly(arylene sulfide), lowmolecular weight poly(arylene sulfide), cyclic and linear poly(arylenesulfide) oligomers, at least one polar organic compound, at least onemodifier, and an alkali metal halide by-product, said processcomprising: 1) contacting said quench process reaction mixture withadditional polar organic compound at a temperature sufficient todissolve substantially all of said low molecular weight poly(arylenesulfide) and cyclic and linear oligomers to produce a quench processpolar organic compound-rich mixture; 2) separating said quench processpolar organic compound-rich mixture to produce a quench process solidstream and a quench process liquid stream; wherein said quench processsolid stream is in a substantially solid form and comprises said highmolecular weight poly(arylene sulfide), polar organic compound, aportion of said modifier compound, and a portion of said alkali metalhalide by-product; wherein said quench process liquid stream is in asubstantially liquid form and comprises substantially all of said lowmolecular weight poly(arylene sulfide) and cyclic and linearpoly(arylene sulfide) oligomers, polar organic compound, a portion ofsaid modifier compound and a portion of said alkali metal halideby-product; 3) contacting said quench process solid stream with methanolto produce a quench process methanol-rich high molecular weightpoly(arylene sulfide) product mixture; 4) separating said quench processmethanol-rich high molecular weight poly(arylene sulfide) productmixture to produce a high molecular weight poly(arylene sulfide) productand a first recycle mixture stream; wherein said first recycle mixturestream comprises methanol, polar organic compound, and modifiercompound; 5) contacting said quench process liquid stream with methanolto produce a quench process methanol-rich low molecular weightpoly(arylene sulfide) mixture; 6) separating said quench processmethanol-rich low molecular weight poly(arylene sulfide) mixture toproduce a low molecular weight poly(arylene sulfide) product and asecond recycle mixture stream; wherein said second recycle mixturestream comprises methanol, polar organic compound, and modifiercompound; and wherein said low molecular weight poly(arylene sulfide)product comprises said low molecular weight poly(arylene sulfide) andcyclic and linear poly(arylene sulfide) oligomers; 7) passing said firstand said second recycle mixture streams to a first separation zone toyield methanol and a recycle feedstock mixture; wherein said recyclefeedstock mixture comprises polar organic compound and modifiercompound; and 8) contacting said low molecular weight poly(arylenesulfide) product with water to produce a water-washed low molecularweight poly(arylene sulfide) product and a first alkali metal halideby-product stream; wherein said alkali metal halide by-product streamcomprises water, methanol, and alkali metal halide by-product.
 14. Aprocess according to claim 13 further comprising passing said firstalkali metal halide by-product stream to a second separation zone torecover said methanol and said alkali metal halide by-product.
 15. Aprocess according to claim 14 comprising in addition contacting saidhigh molecular weight poly(arylene sulfide) product with water toproduce a water-washed high molecular weight poly(arylene sulfide)product and a second alkali metal halide by-product stream; wherein saidalkali metal halide by-product stream comprises water, methanol, andalkali metal halide by-product; and passing said second alkali metalhalide by-product stream to said second separation zone.
 16. A processaccording to claim 13 wherein methanol and said recycle feedstock isreused.
 17. A process to recover at least one polar organic compound andat least one modifier from a quench process reaction mixture comprisinghigh molecular weight poly(arylene sulfide), low molecular weightpoly(arylene sulfide), cyclic and linear poly(arylene sulfide)oligomers, at least one polar organic compound, at least one modifier,and an alkali metal halide by-product, said process comprising: 1)contacting a quench process reaction mixture with at least one polarorganic compound at a temperature sufficient to dissolve substantiallyall of said low molecular weight poly(arylene sulfide) and cyclic andlinear oligomers to produce a quench process polar organic compound-richmixture; 2) separating said quench process polar organic compound-richmixture to produce a quench process solid stream and a quench processliquid stream; wherein said quench process solid stream is in asubstantially solid form and comprises said high molecular weightpoly(arylene sulfide), polar organic compound, a portion of saidmodifier compound, and a portion of said alkali metal halide by-product;wherein said quench process liquid stream is in a substantially liquidform and comprises substantially all of said low molecular weightpoly(arylene sulfide) and cyclic and linear poly(arylene sulfide)oligomers, polar organic compound, a portion of said modifier compound,and a portion of said alkali metal halide by-product; 3) contacting saidquench process liquid stream with methanol to produce a quench processmethanol-rich low molecular weight poly(arylene sulfide) mixture; 4)separating said quench process methanol-rich low molecular weightpoly(arylene sulfide) mixture to produce a low molecular weightpoly(arylene sulfide) product and a recycle mixture stream; wherein saidrecycle mixture stream comprises methanol, polar organic compound, andmodifier compound; and wherein said low molecular weight poly(arylenesulfide) product comprises said low molecular weight poly(arylenesulfide) and cyclic and linear poly(arylene sulfide) oligomers; and 5)contacting said low molecular weight poly(arylene sulfide) product withwater to produce a water-washed low molecular weight poly(arylenesulfide) product and an alkali metal halide by-product stream.
 18. Aprocess according to claim 17 wherein said poly(arylene sulfide) ispoly(phenylene sulfide) and said polar organic compound is NMP.
 19. Aprocess to recover at least one polar organic compound and at least onemodifier from a quench process reaction mixture comprising highmolecular weight poly(arylene sulfide), low molecular weightpoly(arylene sulfide), cyclic and linear poly(arylene sulfide)oligomers, at least one polar organic compound, at least one modifier,and an alkali metal halide by-product, said process comprising: 1)contacting said quench process reaction mixture with additional polarorganic compound at a temperature sufficient to dissolve substantiallyall of said low molecular weight poly(arylene sulfide) and cyclic andlinear oligomers to produce a quench process polar organic compound-richmixture; 2) separating said quench process polar organic compound-richmixture to produce a quench process solid stream and a quench processliquid stream; wherein said quench process solid stream is in asubstantially solid form and comprises said high molecular weightpoly(arylene sulfide), polar organic compound, a portion of saidmodifier compound, and a portion of said alkali metal halide by-product;wherein said quench process liquid stream is in a substantially liquidform and comprises substantially all of said low molecular weightpoly(arylene sulfide) and cyclic and linear poly(arylene sulfide)oligomers, polar organic compound, a portion of said modifier compound,and a portion of said alkali metal halide by-product; 3) contacting saidquench process solid stream with methanol to produce a quench processmethanol-rich poly(arylene sulfide) product mixture; 4) separating saidquench process methanol-rich poly(arylene sulfide) product mixture toproduce a high molecular weight poly(arylene sulfide) product and afirst recycle mixture stream; wherein said first recycle mixture streamcomprises methanol, polar organic compound, and modifier compound; 5)contacting said quench process liquid stream with methanol to produce aquench process methanol-rich low molecular weight poly(arylene sulfide)mixture; 6) separating said quench process methanol-rich low molecularweight poly(arylene sulfide) mixture to produce a low molecular weightpoly(arylene sulfide) product and a second recycle mixture stream;wherein said second recycle mixture stream comprises methanol, polarorganic compound, and modifier compound; and wherein said low molecularweight poly(arylene sulfide) product comprises said low molecular weightpoly(arylene sulfide) and cyclic and linear poly(arylene sulfide)oligomers.
 20. A process according to claim 19 further comprisingseparating said first and second recycle mixture streams in a separationzone to yield methanol and a recycle feedstock mixture.
 21. A processaccording to claim 16 wherein methanol and said recycle feedstock isreused.